In 3GPP (3rd Generation Partnership Project) which is a project aiming to standardize a mobile communication system, specifications of LTE (Long Term Evolution) and LTE Advanced, which is a sophisticated version of LTE, have been designed in order to perform higher speed communication with larger capacity.
In such a mobile communication system, in order to reduce a ratio of a header to a packet transmitted and received via a radio space, that is, an overhead, a ROHC (Robust Header Compression) protocol, which is one of the header compression technologies, is used (see Non Patent Literature 1). According to the ROHC protocol, it is possible to compress a packet header of various formats, such as IP (Internet Protocol), UDP (User Datagram Protocol), or RTP (Real-time Transport Protocol), up to 1 byte
In the header compression technology, each of a radio terminal and a base station constructs header-related information on the basis of a packet to be transmitted and received, and perform header compression and decompression for the packet transmitted and received via a radio space by using the header-related information shared between the radio terminal and the base station. In such a header compression technology, as the header-related information is being constructed in the radio terminal and the base station, it is possible to sequentially increase a header compression level. The header-related information in the ROHC protocol is called ROHC context.